Cultivating mushrooms and producing soil amendments using underutilized waste materials to increase profitability in an agroforestry system.

View the project final report

Commodities

• Miscellaneous: mushrooms

Practices

• Crop Production: agroforestry
• Education and Training: mentoring
• Energy: byproduct utilization
• Farm Business Management: apprentice/intern training, farmers' markets/farm stands, new enterprise development
• Production Systems: permaculture
• Soil Management: composting, earthworms, organic matter, soil quality/health

The purpose of this project is to increase capacity for mushroom production as a way to convert underutilized, on-farm resources into a nutritious product, while improving soil health, and increasing profitability in an agroforestry system. Mushroom cultivation can play a key role in our system by providing a consistent weekly marketable yield, with low input costs and next to zero waste. For agroforestry to be financially viable for farmers, there must be streams of revenue during the years before the trees and woody perennials reach maturity. Mushroom cultivation provides a relatively secure path to profit during this vital interim and beyond. The spent mushroom substrate (i.e. the “waste” material that remains after mushroom harvest) will be used in a vermicompost system, supporting the production of worm castings, a high quality soil amendment. This vermicompost can be combined with biochar (which can be produced on-site from agroforestry waste products) to produce a biodiverse soil amendment that can improve soil health and plant yields throughout the agroforestry system. Biochar paired with vermicompost has shown to provide synergistic benefits (Doan et al, 2015). With further development, this amendment can become a marketable product in its own right, supporting horticulture, urban farming, and container gardening. 

As a research component of this project, we compared two methods of straw substrate pasteurization with an unpasteurized control.  The two treatment methods we used were soaking straw 12-24 hours in a solution of hydrated lime (pH 12+) and soaking straw in the squelch water from biochar burns (supplemented with lime when necessary to raise pH to 12+).  Detailed pasteurization protocols are linked in this report.

We experimented with six varieties of commercially available oyster mushrooms.  We found four varieties that worked well for us throughout all seasons, and two that were successful in the warmer seasons.  While two varieties were the most prolific, we found that our customers appreciate variety, and continue to offer 4-6 varieties depending on the season. On land utilized in agroforestry practices, native oyster mushroom strains were found which, with proper inoculation procedures, could increase production rates while reducing input costs.

We also experimented with different methods of utilizing spent substrate, including: building outdoor mushroom beds that incorporated fresh substrate for additional fruiting;  vermicompost; incorporating into garden scrap compost; incorporating into cow manure-based compost.  

The timeline, scale and nature of this project yielded more observational data than statistically significant quantitative data.  

We found that both hydrated lime and biochar squelch water provided the benefits of substrate pasteurization.  To our knowledge, this project was the first to demonstrate that biochar squelch water can be used in this way, and we would recommend the practice to other small-scale operations.

All forms of spent substrate management effectively turned the spent straw into useful products for our soils.  Our vermicompost did not reach a large enough scale to overwinter, so we kept vermicompost in bins in our greenhouse. While we had success establishing outdoor beds with spent substrate, the mushrooms that were produced in these beds tended to be irregular in shape and size and were often covered in straw.  These mushrooms were not market quality though they were excellent for home consumption.

This project provided numerous educational opportunities for more than 50 farm apprentices over the two years of the project and other practitioners in our community through multiple field days each season.  During the fall of the second year of the project, we hosted a mushroom cultivation field day where participants engaged in all aspects of the cultivation process and made their own grow bags to take home.

The farm now has an established growing system.  We will continue to grow mushrooms in future seasons, providing learning opportunities for apprentices and community members, as well as providing food and revenue for the farm operation.

1. Build infrastructure to support mushroom cultivation including a transfer space, incubation room, and fruiting room.
2. Refine and document mushroom cultivation standard operating procedures by end of 2022.
3. Grow and sell an average of 30 lbs of mushrooms per week for 30 weeks throughout the 2023 growing season.
4. Develop a healthy compost system to match the scale of mushroom production and utilize compost in farm operations.
5. Develop teaching tools to support apprenticeship education on mushroom cultivation and vermicompost.
6. Document and share findings through social media and field days.